No power past 1/3 throttle


Information and questions on GL1200 Goldwings (1984-1987)
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1200Doug
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Location: Long Island, NY
Motorcycle: 1986 GL1200 Interstate

No power past 1/3 throttle

Postby 1200Doug » Thu Jul 16, 2015 5:23 pm



I just purchased a 1986 Interstate with 27k miles. Previous owner did a bunch of work just refereshing and polishing it up. Rebuilt the carbs twice using an ultrasonic cleaner. The second time around the bike ran a bit worse than the first.

The problem is past 1/3 throttle it has no power on the road.

It starts right up 90% of the time like a new machine. The other times it cranks and cranks without so much as a hint of catching.

It revs up to 8k in neutral but labors to do so.

Idles beautifully.

Any ideas?


It's a fine line between hobby and mental illness

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virgilmobile
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Re: No power past 1/3 throttle

Postby virgilmobile » Thu Jul 16, 2015 10:47 pm

First verify there's enough battery volts while running..It must stay above 13.2 and not go above 14.5
Second,if the volts are fine,add a bit of choke when it's laboring....see if it improves or gets worse...
Third..pull the plugs for a quick look...there condition will tell if a cylinder is running rich or lean or just right...
Fourth..Stick a mirror in the plenum box...get a eyeball on the slides..rap the throttle and verify that they do rise and fall with the rpm..
Fifth...when it's laboring,reach around and shut off the fuel then kill the ignition...drain each carb bowl..see how much fuel is in each carb...there could be a poor pump,plugged fuel filter or poor fuel supply front the tank,eg rusted causing fuel starvation

Just a few things to check...
The engine must have good spark,good compression,able to breathe a lot of air and get rid of the exhaust.If any one of these ,including fuel mixture is dampered..it won't run right..

So,as they say,divide and conqure...identify what does work from what does not...3 sections..Spark,compression and fuel...Then attack the one problem..Do not assume that any work previously done by anybody is flawless.Verify it.
Case in point..."they have been worked on twice and the second time it's worse"...

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maintainer
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Motorcycle: 1977 GL 1000
1982 GL 1100 Interstate (Sold)

Re: No power past 1/3 throttle

Postby maintainer » Fri Jul 17, 2015 7:20 am

What he said ^ , excellent troubleshooting advice.
1982 GL 1100 Interstate SOLD
1977 GL 1000 Standard (naked can be good, who knew?)

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1200Doug
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Motorcycle: 1986 GL1200 Interstate

Re: No power past 1/3 throttle

Postby 1200Doug » Fri Jul 17, 2015 2:22 pm

Thank you SO much for the advice.
I have some questions to help guide me:
1) I measure the voltage at the battery correct?
2) when I pull the plugs do I shut down the bike with the throttle open first or just after a regular shut down? (I know not to pull the plugs too hot so as not to gall to threads)
3)plenum box: is that the air box? Slides? I've only seen them on a schematic but not in reality. I guess they're black and cylindrical and readily apparent?
4)do you want me to measure the amount of fuel in each bowl and how accurate do you need? Or am I just verifying they have equal amounts and "a half shot glass"

Sorry to answer your questions with questions. I just won't have a chance to get my hands dirty until at least tomorrow and want to make sure I can report back definitively.

Thanks again.
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virgilmobile
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83 GL1100 I
83 GL1100 standard
84 GL 1200 I

Re: No power past 1/3 throttle

Postby virgilmobile » Fri Jul 17, 2015 5:16 pm

Regular shut down..cold engine..this can be the first look to see how each cylinder is running,then put them back.
yes on the volt test,at the battery while running
Air box,plenum...same..with the mirror at a angle..possibly with a flashlight.
Fuel...not accurate..just to see if all 4 have enough fuel to run the bike.it should have the same amount at a idle or at 5k rpm..

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1200Doug
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Motorcycle: 1986 GL1200 Interstate

Re: No power past 1/3 throttle

Postby 1200Doug » Sun Jul 19, 2015 2:57 am

I ran into the no start problem and killed the battery after several attempts.

I'm trickle charging it back up now.

I noted after turning the throttle 2/3 of the way once for a literal second the bike immediately stunk of gas. Not sure if that's normal I've gotten accustomed to fuel injection bikes.

In the meantime I pulled the plugs.
Plugs
Plugs

Most notable: right rear is sooty and left front stunk of fuel.

At this point should I halt further diagnostics to rebuild the carbs to prevent damage from gas scrubbed cylinder walls?
And what is the liklihood these carbs aren't in fact rebuildable?

Gas in one cylinder says to me either the float is misadjusted or the gas cutoff bit of rubber is damaged. But it's also possible the pivot is hanging things up. Might it also be possible the mixture screw is just set incredibly rich?
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flash1942
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Re: No power past 1/3 throttle

Postby flash1942 » Sun Jul 19, 2015 8:59 am

After going thru my carbs for the 2nd time (ugh) I found that the needle jet(the pressed in one) was clogged. The motor would miss,pop, backfire on that cyl. I ran a fine wire thru the jet and it now runs wonderfully.

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1200Doug
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Re: No power past 1/3 throttle

Postby 1200Doug » Mon Jul 20, 2015 6:22 pm

flash1942 wrote:After going thru my carbs for the 2nd time (ugh) I found that the needle jet(the pressed in one) was clogged. The motor would miss,pop, backfire on that cyl. I ran a fine wire thru the jet and it now runs wonderfully.


Yes if all signs are fuel I'll look there too for sure good idea. I'm hoping its something simple ultimately!
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flash1942
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Re: No power past 1/3 throttle

Postby flash1942 » Tue Jul 21, 2015 9:28 am

I determined mine to be a fuel problem by using the choke at lower speeds until it(choke) ran out of it's designed operating range. I might add that you may want to check the floats for weight difference due to internal leakage. Preset all the idle screw jets,check the needle jets and lastly consider upping the low speed jets to one size larger as it will help throttle response. I might say here that all of the advice has been very good . good luck.

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1200Doug
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Re: No power past 1/3 throttle

Postby 1200Doug » Tue Jul 21, 2015 12:34 pm

I just put new plugs in and checked voltage which was 14.5/14.6.
Bike fired right up.
Revved it up to 8k easier than before although it was popping around 6-8k occasionally in spurts.
Didn't get a chance to test ride it. Am thinking of throwing Berryman B12 in the fuel to help clean out any residue that might be clogging things. Really want to continue with the diagnostics as outlined. Working too much but that's NY for you.
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1200Doug
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Re: No power past 1/3 throttle

Postby 1200Doug » Thu Jul 23, 2015 1:17 pm

Update: the bike shows 14.5/14.6 at idle. When revving it up to 5/6k it hits 15.10. Do I need a new regulator?

I took her out for a spin. Lots of stutters on acceleration around 5k and quite down on power above 4k with popping on deceleration. Choke eliminate some of the popping but overall the bike feels like it's on 3 cylinders due to rough running, no top end, etc.

Should I check the coils? How is that done?

I spoke to the guy that wrote the carb rebuild manual that Randakk sells. He said it sounds like an air cutoff valve issue. I ordered the rebuild kit and manual. Saturday I'm tearing into the carbs.
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maintainer
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1982 GL 1100 Interstate (Sold)

Re: No power past 1/3 throttle

Postby maintainer » Thu Jul 23, 2015 3:19 pm

1200Doug wrote:Update: the bike shows 14.5/14.6 at idle. When revving it up to 5/6k it hits 15.10. Do I need a new regulator?


I would say so, regulator seems out of spec 15.10 could boil the battery dry. I don't have the service manual spec in front of me but I think about 13.1 vdc at idle and 14.5 vdc at max speed is closer to normal.
Sounds like you need a new regulator.
1982 GL 1100 Interstate SOLD
1977 GL 1000 Standard (naked can be good, who knew?)

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virgilmobile
Posts: 7660
Joined: Sun Sep 19, 2010 5:39 pm
Location: Denham Springs,La.
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78 GL1000
81 GL1100
82 GL1100 I
83 GL1100 I
83 GL1100 standard
84 GL 1200 I

Re: No power past 1/3 throttle

Postby virgilmobile » Thu Jul 23, 2015 3:51 pm

Over 15 volt is out of specs but I doubt that the regulator is at fault.If you want to test it,Get it running with a DVM attached to the battery,Temporarily attach a wire from the positive battery post directly to the small black wire going into the regulator.Its suppose to be switched ignition.You should see the voltage drop below 14.4 right away.
This is a common voltage drop problem in switched ignition wiring.The voltage loss or drop is from old wiring and switching.Should it drop to normal,a bypass relay can be added to that circuit to stop the over voltage/charge issue.
That black wire is suppose to represent the battery volts and I usually find that it measures from 0.5 to over 1.5 volts different.

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1200Doug
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Motorcycle: 1986 GL1200 Interstate

Re: No power past 1/3 throttle

Postby 1200Doug » Thu Jul 23, 2015 5:14 pm

virgilmobile wrote:Over 15 volt is out of specs but I doubt that the regulator is at fault.If you want to test it,Get it running with a DVM attached to the battery,Temporarily attach a wire from the positive battery post directly to the small black wire going into the regulator.Its suppose to be switched ignition.You should see the voltage drop below 14.4 right away.
This is a common voltage drop problem in switched ignition wiring.The voltage loss or drop is from old wiring and switching.Should it drop to normal,a bypass relay can be added to that circuit to stop the over voltage/charge issue.
That black wire is suppose to represent the battery volts and I usually find that it measures from 0.5 to over 1.5 volts different.


I'm sorry this is a bit over my head- not the diagnostics just what exactly the switching issue is? Where can I find more info? Is there a name for this mod? Also is it vital I tackle this right away? I want to use the bike but don't want to fry the new battery or anything!
It's a fine line between hobby and mental illness

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maintainer
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Motorcycle: 1977 GL 1000
1982 GL 1100 Interstate (Sold)

Re: No power past 1/3 throttle

Postby maintainer » Thu Jul 23, 2015 6:11 pm

I checked the service manual, I was wrong. :shock: Max output of 15 VDC is max but acceptable, who knew. So evidently even though you are at the high end of the specified range, you should be fine.
1982 GL 1100 Interstate SOLD
1977 GL 1000 Standard (naked can be good, who knew?)

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1200Doug
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Motorcycle: 1986 GL1200 Interstate

Re: No power past 1/3 throttle

Postby 1200Doug » Sat Jul 25, 2015 8:53 pm

Ok carbs out, gas tank out, going to look into re-chroming or powdercoating some bits. And while I'm at it I think I'll do timing belts and figure out why my exhaust is leaking where the pipes meet the mufflers.

Supposed to be new gaskets in there but based on all the barely tightened fastners, cut fuel hose and cracked vacuum hose I'm not surprised. Can't believe someone got paid to do work like this.

I did notice the vacuum line disconnected that goes from #4 intake to the air cut off valve. Could that be the source of my poor top end performance?
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1200Doug
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Motorcycle: 1986 GL1200 Interstate

Re: No power past 1/3 throttle

Postby 1200Doug » Sat Aug 01, 2015 10:47 pm

Carb rebuild nearly complete.

Found my problems:

Left front carb (#2) blocked idle jet

Left rear carb (#4) idle mix screw snapped off in body and jet needle diaphragm/vacuum piston not seated properly

# 4 intake vacuum hose (not the secondary air supply lines) possibly disconnected before pulling carb manifold out of bike

Intake manifold boots not tightened fully

Various vacuum lines may be leaky


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